if all u did was the extension

and you hadn't received any payment or worked without EAD, then you haven't really done anything illegal. And just by extending your I-20, the school shouldn't be in any trouble either,because it seems to be a gray area of the law that is open to interpretation.

The important thing is that you should be OPEN with them. They are not your enemy and you don't want to give them the impression that you want to hide something.

Either way, it shouldn't affect your hu*****and.